On 7/7/2018 10:27 AM, Emanuel Berg wrote:
Are there any secrets to drilling holes in
steel bike frames? I have a couple of discarded
ones I can test on but I thought I'd
ask anyway.

Do you use normal power hand tools like
a drill-screwdriver and/or a drill press (if
possible with the desired bolt position)?

Do the normal rules apply, e.g. to get
a threaded hole for an M6, you first drill with
a 5.0mm drill?

And you can use chainsaw oil, right?

Exactly what are you planning to attach, and where?

If you're drilling and tapping in (say) rear dropouts, normal practices
should be fine. But if you're planning on drilling and tapping frame
tubes, you probably wont' have sufficient wall thickness in the tubes.

It's usually considered proper to give tapped holes a thread depth at
least 1.5 times the screw diameter. So for a 5mm screw, you'd want 7.5mm
of thickness. Sometimes a little less can be OK. But your frame tube
walls are probably less than 1mm thickness. That's not enough.

This group has debated Rivnuts extensively. One poster claims nobody
should install a Rivnut unless he has access to a complete machine shop.
Others with more experience have said that the installation is easy for
anyone with normal mechanical skills.

Frank Krygowski wrote:
If you're drilling and tapping in (say) rear
dropouts, normal practices should be fine.
But if you're planning on drilling and
tapping frame tubes, you probably wont' have
sufficient wall thickness in the tubes.

It's usually considered proper to give tapped
holes a thread depth at least 1.5 times the
screw diameter. So for a 5mm screw, you'd
want 7.5mm of thickness. Sometimes a little
less can be OK. But your frame tube walls are
probably less than 1mm thickness.
That's not enough.

The stays that hold the chainguard, both from
the front and under, are very thin, probably
around 1mm. Still it is enough for a couple of
Torx flat-headed M5 screws to hold it (1 from
under, 2 front, the one at the rear is usually
bolted tho with a nut on the other side).

The down stay is also fastened in the same way
to the frame. (I don't know how the front one
is attached because you typically don't remove
it. But I'll check it out.)

On 7/7/2018 9:27 AM, Emanuel Berg wrote:
Are there any secrets to drilling holes in
steel bike frames? I have a couple of discarded
ones I can test on but I thought I'd
ask anyway.

Do you use normal power hand tools like
a drill-screwdriver and/or a drill press (if
possible with the desired bolt position)?

Do the normal rules apply, e.g. to get
a threaded hole for an M6, you first drill with
a 5.0mm drill?

And you can use chainsaw oil, right?

From playing with the metalworking machines I have...

1) A drill press w/vise will work far better than a hand drill. If you
use a hand drill in thicker (1mm) metal, the bits will go dull really
fast and tend to break as they come out the back side of the hole.

2) there are tap/drill charts online that tell you what hole size is
needed for which tap size.

3) for cutting fluid--real fluid is best but any lubricating oil you
have is way better than nothing.

4) cheap taps tend to be really ****ty--there's no other word for it.
The metal is weak, the thread fit is loose and even with lube they are
hard to turn in (being ground poorly),,, which makes breaking them even
more likely. They aren't worth stealing.

But good taps,,, cost money (just like drill bits). The $50 set at Sears
would cost you $400+ from a real machinist supply place. I would suggest
you buy a single spiral-point tap online, as you need them.

5) and you didn't ask, but just FYI: stainless steel is a royal bitch.
It is way, way, way tougher than carbon steel. Other than an angle
grinder, cheap tools simply won't cut it. You pretty much need a BIG
drill press or mill and good cobalt/carbide drill bits w/real cutting
fluid.

I have seen posts online where people wanted to drill a hole in a cheap
stainless-steel mixing bowl, and they couldn't figure out why the drill
bit would just spin around and not go through.

Jeff Liebermann

July 7th 18 08:08 PM

drill/tap in frames

On Sat, 07 Jul 2018 16:27:01 +0200, Emanuel Berg
wrote:
Are there any secrets to drilling holes in
steel bike frames? I have a couple of discarded
ones I can test on but I thought I'd
ask anyway.

Do you use normal power hand tools like
a drill-screwdriver and/or a drill press (if
possible with the desired bolt position)?

Use a drill press and a tubing drilling jig. I use one of these:
https://www.trick-tools.com/Center_It_Drill_Jig_CI_1_1154
I've had bad luck using an electric drill. A drill press (or vertical
mill) is best.
Do the normal rules apply, e.g. to get
a threaded hole for an M6, you first drill with
a 5.0mm drill?

The tubing is probably too thin for threading the hole. You need at
least 3 full threads wall thickness tubing to keep the mounting screw
from stripping the threads out of the hole. For an M5x0.8, that's 0.8
mm per thread. So, the minimum tubing wall thickness would be 2.4mm.
However, since the tubing on your bicycle is probably around 0.5mm
wall thickness, the tubing wall will never be thick enough to support
threading. To get more threads to grip is one reason why builders use
braze on bosses for mount points.

You should have a drill chart available. Print one and hang it
somewhe
https://www.google.com/search?q=tap+and+drill+chart&tbm=isch
And you can use chainsaw oil, right?

Maybe. High tack oil can be applied to the boss and left to harden
into a passable glue. In a few months, it should be sufficiently
hardened to support an empty water bottle for a few miles before it
falls off.

On Sat, 7 Jul 2018 11:06:52 -0400, Frank Krygowski
wrote:
This group has debated Rivnuts extensively. One poster claims nobody
should install a Rivnut unless he has access to a complete machine shop.
Others with more experience have said that the installation is easy for
anyone with normal mechanical skills.

That would be SMS (Steven Scharf) on one of his web pages:
http://nordicgroup.us/cageboss/

Since I've made a mess with all the available technologies, Rivnuts
(steel and aluminum), brazing (steel), TIG (aluminum), and epoxy glue
(plastic boss on aluminum), I'll remain neutral on the matter.

Doug Cimperman wrote:
1) A drill press w/vise will work far better
than a hand drill. If you use a hand drill
in thicker (1mm) metal, the bits will go
dull really fast and tend to break as they
come out the back side of the hole.

Drill bits, is there a reason to use those
instead of just drills (round)?
2) there are tap/drill charts online that
tell you what hole size is needed for
which tap size.

Jeff Liebermann wrote:
The tubing is probably too thin for threading
the hole. You need at least 3 full threads
wall thickness tubing to keep the mounting
screw from stripping the threads out of the
hole. For an M5x0.8, that's 0.8 mm per
thread. So, the minimum tubing wall thickness
would be 2.4mm. However, since the tubing on
your bicycle is probably around 0.5mm wall
thickness, the tubing wall will never be
thick enough to support threading. To get
more threads to grip is one reason why
builders use braze on bosses for
mount points.

I keep hearing this, but it isn't the case for
my bikes which have chainguards.

These have three stays, and of those, two are
mounted on the bike frame with M5 screws.
Threaded hole, no nut on the other side!

Then the chainguard is mounted on the stays,
likewise with M5s, threaded holes (only here
sometimes there are nuts as well).

The stays are about 1mm. How thick the frame
tube wall is I don't know, but I can take
a discarded frame and cut it with an angle
grinder to find out, God willing.

This ain't to say that rivnuts ain't a good
idea, of course.

BTW, do you by them online? I don't think they
are in our HW stores... (which is common with
the stuff you guys mention: durometer, soft jaw
pliers, etc.)